In marine applications, hydraulic systems are known which cool marine engines by piping water directly from the sea along an intake pipe fitted with a safety valve which, in an emergency, can be operated manually or by means of an actuator to cut off the flow of seawater.
As is known, such valves comprise a control member, e.g. a handwheel or lever, outside the intake pipe; and a shutter, e.g. a ball or gate, operated by the control member with the interposition of a transmission. Being subject to continual aggression, oxidation, and/or erosion by the seawater flowing in the system, the transmission eventually tends to seize, thus making it difficult or impossible to close the shutter, especially if the valve is not operated or tested for prolonged periods of time.